Hello!

 

I am going to take a resistance value across the heather wires at the O2 sensor. Do I have to disconnect the O2 sensor before doing this? And should the car be running at idle when I am taking the resitance value?

 

EgilTT

To test the heater wires disconnect the sensor (ignition doesn't need to be on) and check the resistance using a multimeter. I have never seen an O2 sensor with a duff heater, ever. I doubt it that the heaters themselves are duff but the heater supply may be.

To test the heater supply you want the O2 sensors plugged in and engine just started. Test the voltage using a multimeter at the O2 sensor plugs. Again this is very uncommon.

 

Most O2 sensor failures are down to contamination or natural life exceeded. I have never seen a heater fail and rarely seen heater supply problems, I change loads of O2 sensors due to contamination and a few due to old age.

 

SparkZ